(() => {
    class Person {
        constructor(firstName, lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
        }
        get fullName() {
            return this.firstName + '_' + this.lastName;
        }
        set fullName(val) {
            let names = val.split('_');
            this.firstName = names[0];
            this.lastName = names[1];
        }
    }
    let p = new Person('东方', '不败');
    console.log(p.fullName);
    p.fullName = '诸葛_孔明';
    console.log(p.firstName);
    console.log(p.lastName);
    console.log(p.fullName);
    let a = 'aaa';
    let b = a.concat('a', 'b', 'c');
    console.log(b);
})();
